You can buy daily, 2 day, weekly, monthly or annual bus/metro pass.
The metro and buss pass has a monthly charge of 34 euros.
Usually trains and coaches are the best means of travel in France. Train is inexpensive and very efficient. Buying a 12-25 railcard for 54€ cuts the price by 50%.
Toulouse has great access to train lines that cover all European destinations so make the most of it.
Toulouse is also deserved by low cost airplane companies such as Easyjet and Vueling. Planning ahead will give you the chance to get very cheap flight tickets.